Lasers mode locked to a single mode of operation are important in a wide variety of applications such as optical fiber communications and optical test instruments. Indeed single mode lasers are almost indispensable to provide the stable, reliable signals needed in high speed optical communications.
Conventional practice is to use distributed feedback lasers (DFB lasers) for such applications. Unfortunately DFB lasers are difficult to fabricate. The fabrication process is complex, the yields are low and, as a consequence, the lasers are expensive. In addition the lasing wavelength of a DFB laser depends heavily on the ambient temperature and the injected current, presenting issues of output wavelength stability.
Accordingly there is a need for a compact, reliable, low-cost single-mode laser.